refactor: prevent duplicate preload

packages/shared/src/feed-cache.ts

@@ -42,9 +42,12 @@ export abstract class FeedCache<TCached> {
   }
 
   async preload() {
+    // assume already preloaded if keys exist on table in memory
+    if (this.onTable.size === 0) {
       const keys = (await this.table?.toCollection().primaryKeys()) ?? [];
       this.onTable = new Set<string>(keys.map(a => a as string));
     }
+  }
 
   keysOnTable() {
     return [...this.onTable];